AFRICAN cities need to better plan and invest in water infrastructure, global accounting firm Deloitte says, as Cape Town counts down to dry taps from severe drought.

Officials predict taps in the South African city will run out of water on May 11, in a crisis that has brought to the fore the effects of climate change across the world.

"Cape Town is not going to be the only city on this continent that's going to suffer significant water shortage," Jean-Pierre Labuschagne, an infrastructure expert with Deloitte, said at the launch of its Africa Construction Trends report.

Cape Town authorities have imposed water restrictions that could hurt agricultural and industrial output, and have begun to affect tourism.

Labuschagne said high levels of rural to urban migration had made it hard for many cities in Africa to plan well and expand infrastructure fast enough to accommodate increased numbers of people, most of whom ended up living in informal settlements.

In addition, cities like Kenya's Nairobi and Ghana's Accra have suffered recurrent water shortages for years as reservoirs fall to critical levels in the dry season.

Water shortages in these cities threaten the lives of million in places like Kibera in Nairobi - one of Africa's largest slums - where an outbreak of sanitary diseases such as cholera and typhoid could be catastrophic.

"Nairobi's water system was planned for a population of about half a million people, but it now has more than 4 million people," said John Ponsonby, Deloitte's associate director of infrastructure.

"Part of the problem with water is you need to think many years in advance ... You have to be able to cope with changes in climate."